1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/arch/alpha/lib/memcpy.c
4 *
5 * Copyright (C) 1995 Linus Torvalds
6 */
7
8 /*
9 * This is a reasonably optimized memcpy() routine.
10 */
11
12 /*
13 * Note that the C code is written to be optimized into good assembly. However,
14 * at this point gcc is unable to sanely compile "if (n >= 0)", resulting in a
15 * explicit compare against 0 (instead of just using the proper "blt reg, xx" or
16 * "bge reg, xx"). I hope alpha-gcc will be fixed to notice this eventually..
17 */
18
19 #include <linux/types.h>
20 #include <linux/export.h>
21 #include <linux/string.h>
22
23 /*
24 * This should be done in one go with ldq_u*2/mask/stq_u. Do it
25 * with a macro so that we can fix it up later..
26 */
27 #define ALIGN_DEST_TO8_UP(d,s,n) \
28 while (d & 7) { \
29 if (n <= 0) return; \
30 n--; \
31 *(char *) d = *(char *) s; \
32 d++; s++; \
33 }
34 #define ALIGN_DEST_TO8_DN(d,s,n) \
35 while (d & 7) { \
36 if (n <= 0) return; \
37 n--; \
38 d--; s--; \
39 *(char *) d = *(char *) s; \
40 }
41
42 /*
43 * This should similarly be done with ldq_u*2/mask/stq. The destination
44 * is aligned, but we don't fill in a full quad-word
45 */
46 #define DO_REST_UP(d,s,n) \
47 while (n > 0) { \
48 n--; \
49 *(char *) d = *(char *) s; \
50 d++; s++; \
51 }
52 #define DO_REST_DN(d,s,n) \
53 while (n > 0) { \
54 n--; \
55 d--; s--; \
56 *(char *) d = *(char *) s; \
57 }
58
59 /*
60 * This should be done with ldq/mask/stq. The source and destination are
61 * aligned, but we don't fill in a full quad-word
62 */
63 #define DO_REST_ALIGNED_UP(d,s,n) DO_REST_UP(d,s,n)
64 #define DO_REST_ALIGNED_DN(d,s,n) DO_REST_DN(d,s,n)
65
66 /*
67 * This does unaligned memory copies. We want to avoid storing to
68 * an unaligned address, as that would do a read-modify-write cycle.
69 * We also want to avoid double-reading the unaligned reads.
70 *
71 * Note the ordering to try to avoid load (and address generation) latencies.
72 */
73 static inline void __memcpy_unaligned_up (unsigned long d, unsigned long s,
74 long n)
75 {
76 ALIGN_DEST_TO8_UP(d,s,n);
77 n -= 8; /* to avoid compare against 8 in the loop */
78 if (n >= 0) {
79 unsigned long low_word, high_word;
80 __asm__("ldq_u %0,%1":"=r" (low_word):"m" (*(unsigned long *) s));
81 do {
82 unsigned long tmp;
83 __asm__("ldq_u %0,%1":"=r" (high_word):"m" (*(unsigned long *)(s+8)));
84 n -= 8;
85 __asm__("extql %1,%2,%0"
86 :"=r" (low_word)
87 :"r" (low_word), "r" (s));
88 __asm__("extqh %1,%2,%0"
89 :"=r" (tmp)
90 :"r" (high_word), "r" (s));
91 s += 8;
92 *(unsigned long *) d = low_word | tmp;
93 d += 8;
94 low_word = high_word;
95 } while (n >= 0);
96 }
97 n += 8;
98 DO_REST_UP(d,s,n);
99 }
100
101 static inline void __memcpy_unaligned_dn (unsigned long d, unsigned long s,
102 long n)
103 {
104 /* I don't understand AXP assembler well enough for this. -Tim */
105 s += n;
106 d += n;
107 while (n--)
108 * (char *) --d = * (char *) --s;
109 }
110
111 /*
112 * Hmm.. Strange. The __asm__ here is there to make gcc use an integer register
113 * for the load-store. I don't know why, but it would seem that using a floating
114 * point register for the move seems to slow things down (very small difference,
115 * though).
116 *
117 * Note the ordering to try to avoid load (and address generation) latencies.
118 */
119 static inline void __memcpy_aligned_up (unsigned long d, unsigned long s,
120 long n)
121 {
122 ALIGN_DEST_TO8_UP(d,s,n);
123 n -= 8;
124 while (n >= 0) {
125 unsigned long tmp;
126 __asm__("ldq %0,%1":"=r" (tmp):"m" (*(unsigned long *) s));
127 n -= 8;
128 s += 8;
129 *(unsigned long *) d = tmp;
130 d += 8;
131 }
132 n += 8;
133 DO_REST_ALIGNED_UP(d,s,n);
134 }
135 static inline void __memcpy_aligned_dn (unsigned long d, unsigned long s,
136 long n)
137 {
138 s += n;
139 d += n;
140 ALIGN_DEST_TO8_DN(d,s,n);
141 n -= 8;
142 while (n >= 0) {
143 unsigned long tmp;
144 s -= 8;
145 __asm__("ldq %0,%1":"=r" (tmp):"m" (*(unsigned long *) s));
146 n -= 8;
147 d -= 8;
148 *(unsigned long *) d = tmp;
149 }
150 n += 8;
151 DO_REST_ALIGNED_DN(d,s,n);
152 }
153
154 #undef memcpy
155
156 void * memcpy(void * dest, const void *src, size_t n)
157 {
158 if (!(((unsigned long) dest ^ (unsigned long) src) & 7)) {
159 __memcpy_aligned_up ((unsigned long) dest, (unsigned long) src,
160 n);
161 return dest;
162 }
163 __memcpy_unaligned_up ((unsigned long) dest, (unsigned long) src, n);
164 return dest;
165 }
166 EXPORT_SYMBOL(memcpy);
167
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.